Slogans to pay attention to hygiene in rental housing

To put it mildly: Please take care of our common home and don’t litter. Taking care of the surrounding environment can make everyone's life better. (It is more convincing to state the interests from the perspective of the person who throws garbage.) Sternly: littering is prohibited, otherwise fines will be imposed. (Actually, it’s just a scare.) I suggest using a more tactful one for better results.